1. Field of the Invention
The present invention relates to a method used in a wireless communication system and related communication device, and more particularly, to a method of managing cooperating set for coordinated multiple point (CoMP) transmission and reception and related communication device.
2. Description of the Prior Art
A long-term evolution (LTE) system supporting the 3GPP Rel-8 standard and/or the 3GPP Rel-9 standard has been developed by the 3rd Generation Partnership Project (3GPP) as a successor of a universal mobile telecommunications system (UMTS), for further enhancing performance of the UMTS to satisfy increasing needs of users. The LTE system includes a new radio interface and a new radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes multiple evolved Node-Bs (eNBs) for communicating with multiple user equipments (UEs), and communicates with a core network including a mobility management entity (MME), a serving gateway, etc., for Non Access Stratum (NAS) control.
An LTE-advanced (LTE-A) system, as its name implies, is an evolution of the LTE system. The LTE-A system targets faster switching between power states, improves performance at the coverage edge of an eNB, and includes advanced techniques, such as carrier aggregation (CA), coordinated multipoint (CoMP) transmission/reception, UL multiple-input multiple-output (MIMO), etc. For a user equipment and an eNB to communicate with each other in the LTE-A system, the user equipment and the eNB must support standards developed for the LTE-A system, such as the 3GPP Rel-10 standard or later versions.
When the CoMP is configured to a user equipment and multiple transmission points (e.g. a base station, a relay node, a pico eNB, a home eNB, or a remote antenna of abase station), the user equipment may communicate with the transmission points simultaneously, i.e., access a service via all or part of the transmission points. The set of transmission points directly and/or indirectly participating in data transmission to a user equipment in a time-frequency resource is defined as a cooperating set for the user equipment. In general, the transmission points from which the user equipment can reliably receive signals are selected to form the cooperating set for this user equipment.
Usually, the user equipment may move around to different positions within the coverage of the wireless communication system, or even move outside the coverage of the wireless communication system. The channel conditions of the user equipment to the transmission points may vary from time to time such that the link quality in the wireless communication system may not be in an optimized state. Furthermore, when multiple user equipments are involved in the communication system of the CoMP technology, a new user equipment may come or appear in the wireless communication system, or conversely, an original user equipment may move out or be turned off, so the connection services between the user equipments and the transmission points should be adjusted in response to variations of the channel conditions. However, in the prior art, there is no clear method to solve the above issues for CoMP technology. Therefore, there is a need for improvement of the prior art.